It is well known to prefabricate building panels having rigid frame members and expanded foam material disposed therein. In these particular prior art processes, the frame members are first disposed in a particular way, adhesive material is applied to the frame members and foam is then placed within the frame structure contiguous to the adhesive material. In some processes, no adhesive material is used.
The field of prefabricated building panel construction is extremely crowded. An enormous amount of work has been done in this area of the building industry for cutting costs and maintenance. Many types of foamed plastic materials are known to be useful in the area of building panel construction with foamed polyurethane being most readily used. However, there are numerous disadvantages associated with this material, e.g., it is impossible to obtain a smooth continuous surface on polyurethane foamed with a nozzle. Thus, such foamed material must be cut and shaped in subsequent processing steps.
In U.S. Pat. No. 3,697,633, the frame interior is coated with an epoxy material which is different from the expanded polymer disposed therein. While the expanded polymer is setting, the exothermic heat is sufficient to soften the epoxy and thereby bond the expanded material to the epoxy coated frame members. In this particular process, polyurethane expanded through a conventional foam depositing nozzle provides the desired exothermic heat. The epoxy adhesive is activatible at the temperatures below the expansion temperatures of the polymer being used to fill the frame member. The resultant bond between the polyurethane and frame members has been found to be unsatisfactory.
In U.S. Pat. No. 3,258,889, a polyurethane material is sprayed and foamed within a frame in the conventional manner. The polyurethane foam is said to adhere tenaciously to the frame members. However, subsequent prior art has found it necessary to improve this structure by placing adhesive material on the frame members before spraying the polyurethane into place.
U.S. Pat. No. 3,736,715 discloses the use of a molded polystyrene sheet that is bonded to the frame members in a particular fashion using a peripheral casing assembly. A synthetic plastic adhesive is used to bond glass fiber fabric to the polystyrene sheet. This type of building panel requires considerable handling and construction in order to obtain desirable structural characteristics of a building panel.
U.S. Pat. No. 3,785,913 discloses a panel having an inner skin of material bonded to the outer surface of the frame members. Plastic foaming material such as urethane is then sprayed or poured on top of the inner skin in liquid form between the frame members. No adhesive is used on the frame members in this particular structure. A further layer of compressible material such as fiberglas is then placed on top of the foam. In other words, this foam material requires additional layers on the outside of the frame members to hold the material between the frame members in place. U.S. Pat. No. 3,159,882 shows a building panel having expanded polystyrene bonded to an outside covering for the panel structure.
U.S. Pat. No. 2,972,559 discloses a method of making laminated panels wherein adhesive material bonds an outer board to an expanded polystyrene core. A particular type of solvent adhesive is used to enhance the bond between the core material and the facing member or sheet.
U.S. Pat. No. 3,116,349 teaches a method of molding a laminate comprised of a layer of dense material bonded to a layer of foam styrene polymers without the use of an additional adhesive. Here, a complicated process of partially expanding beads, crushing particles and further subjecting the particles to heat for further expansion is required. There is no structure or process shown in this prior art wherein a rigid frame member can be satisfactorily bonded to a rigid frame member without the use of adhesive materials or some complicated combination of process steps.
U.S. Pat. No. 3,605,365 shows the use of a steam charged mold cavity wherein polystyrene beads may be expanded to form a shaped section. Suitable adhesives may be applied on hard surfaces for bonding during or after molding of the polystyrene beads. Panels of a sandwich type of construction are manufactured by expanding the polystyrene beads between two preshaped faces. The faces are precoated with a rubber or resin. The resultant building panel requires further expansion of the polymer at the building site. There are many attendant disadvantages associated with such a building panel construction.
Finally, for over thirty years, it has been known to unite polystyrene to other surfaces such as metal, glass, wood and the like, by applying a solvent which forms a sticky film on the solid body and then pressing the polystyrene against that film. U.S. Pat. No. 2,628,180 discloses the use of an adhesive composed of styrene monomer which is a very effective solvent for dissolving the expanded polystyrene body. An evaporation retarding material is added to the styrene monomer. The adhesive is then applied with a small syringe or an eye dropper to wet the assembly to which the polystyrene is to be attached.